U.S. Pat. Nos. 3,883,522 and 3,984,548 describe 9-fluoro-3-methyl-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine-6- carboxylic acid, Japanese Patent application (OPI) No. 138582/1979 describes 1-ethyl-6-fluoro-4-oxo-1,4-dihydro-7-(4-methyl-1-piperazinyl)qui noline-3-carboxylic acid, and Japanese Patent Application (OPI) No. 76875/1980 describes 8-(4-methyl-1-piperazinyl)-9-fluoro-5-methyl-6,7-dihydro-1-oxo-1H,5H-benz[ ij]quinolidine-2-carboxylic acid (the term "OPI" as used herein refers to a "published unexamined patent application").